US President Joe Biden says he dropped out of his re-election bid because he feared that the intraparty battle over his candidacy would be a "real distraction" for Democrats and that his highest priority was to defeat Donald Trump in November.

In his first interview since quitting the race, Mr Biden, 81, said he had “no serious problem” with his health. He blamed his poor debate performance on being sick at the time, and brushed off concerns about his age and mental acuity.